1. Field of the Invention
This invention relates in general to a mass storage systems for computer systems, and more particularly to an improved dual actuator pivot bearing system and method for making the same.
2. Description of Related Art
Fixed magnetic disk system, typically referred to as xe2x80x9chardxe2x80x9d disk drives, are now commonplace as the main non-volatile storage in modern personal computers, workstations, and portable computers. Such hard disk drives are now capable of storing gigabyte quantities of digital data, even when implemented in portable computers of the so-called xe2x80x9cnotebookxe2x80x9d class. Many important advances have been made in recent years that have enabled higher data density and thus larger storage capacities of hard disk drives, and that have also enabled much faster access speeds, both in the bandwidth of data communicated to and from the hard disk drive, and also in the access time of specified disk sectors. Advances have also been made that have greatly reduced the size and weight of hard disk drives, particularly as applied to portable computers, have been made over recent years. These advances have resulted in the widespread availability of ultra-light portable computers, yet having state-of-the art capability and performance.
A head/disk assembly typically comprises one or more commonly driven magnetic disks rotatable about a common spindle and cooperating with at least one head actuator for moving a plurality of heads radially relative to the disks so as to provide for the reading and/or writing of data on selected circular tracks provided on the disks. As track pitch decreases, servo performance will decrease because of the more stringent tracking criteria unless a break is made with current disk drive design. One proposal has been to put two independently controlled actuators on one disk drive. Servo performance is then increased because one actuator can seek to a new location while the second actuator is accessing data. In this way the seek and settle time is hidden from the user: he sees instead only the final portion of the seek that occurs when the data access on the other actuator has completed.
However, prior designs for dual actuator pivots have present several manufacturing problems. One problem with prior dual actuator pivot designs is that they have twice as many sleeves and ball bearings as a standard pivot. Outgassing potential is doubled because ball bearings are adhesively bonded to the shaft and sleeve. In addition, with twice as many adhesive joints the risk is doubled of having an adhesive bond fail with catastrophic results to the file. Yet another problem is the assembly time. Because a dual actuator pivot requires the assembly steps equivalent to two pivots, it naturally take twice as long to assemble.
It can be seen then that there is a need for a dual actuator pivot bearing system and method for making the same, wherein the need for adhesive bonding is eliminated and assembly time is minimized.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses an improved dual actuator pivot bearing system.
The present invention solves the above-described problems by press fitting the components of a dual actuator pivot bearing system, including the bearings, shaft and sleeves so that the need for adhesive bonding is eliminated and assembly time is minimized.
A system in accordance with the principles of the present invention includes at least one rotatable disk, at least first and second separately movable heads for providing transducing action with respect to the disk, first and second head actuators, wherein the first head actuator provides radial movement of said first head relative to said disk and said second actuator provides radial movement of said second head relative to said disk, the radial movement provided by each actuator being separately controllable from that of the other actuator, a dual actuator pivot for mounting the first and second actuators, the dual actuator pivot further comprising a first and a second actuator bearing assembly press fitted to a shaft, for rotatably securing the first and second head actuators respectively and at least one controller, operatively coupled to the first and second head actuators for controlling the movement of the first and second head actuators about the dual actuator pivot, the at least one controller producing control signals to control the movement of the first and second actuators.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the first and a second actuator bearing assemblies further comprise an upper sleeve having an upper and lower ball bearing press fitted into a top and bottom bore of the upper sleeve respectively to form the first actuator bearing assembly and a lower sleeve having an upper ball bearing press fitted into a top bore of the sleeve to form the second actuator bearing assembly, the first and second actuator bearing assemblies being press fitted to a shaft assembly comprising a shaft having a ball bearing press fitted at a shaft base.
Another aspect of the present invention is that the system further includes a spacer disposed between the first and second actuator bearing assemblies.
Another aspect of the present invention is that the first and second actuator bearing assemblies are press fitted using a predetermined axial load.
Another aspect of the present invention is that the predetermined axial load is tuned to select a desired resonance frequency for the first and second actuator bearing assemblies.
Another aspect of the present invention is that the shaft comprises steps.
Another aspect of the present invention is that the steps are selected to have diameters matching bearing bore diameters graded from large to small going from a first end of the shaft to a second end of the shaft.
Another aspect of the present invention is that the steps match bearing bore diameters graded from large to small going from the bottom to the top of the shaft so that the bearings at the bottom of the shaft do not produce high frictional forces against the full length of the shaft during assembly.
Another aspect of the present invention is that the shaft is a flangeless shaft comprising large diameter areas formed at a first and second end of the shaft and a reduced diameter area between the large diameter areas.
Another aspect of the present invention is that the large diameter areas provide a interference press fit with the upper ball bearing press fitted into the top bore of the upper sleeve and with the ball bearing press fitted at the shaft base and provide a snug slip fit at the reduced diameter area for the lower ball bearing press fitted into the bottom bore of the upper sleeve and the upper ball bearing press fitted into a top bore of the lower sleeve.
In another embodiment of the present invention, a dual actuator pivot is provided. The dual actuator pivot includes a first and a second actuator bearing assembly press fitted to a shaft for rotatably securing the first and second head actuators respectively.
In another embodiment of the present invention, a method for forming a dual actuator pivot is provided. The method includes press fitting a first ball bearing onto a shaft to make a subassembly, press fitting a second ball bearing into a top bore of a first sleeve to make subassembly, press fitting a third ball bearing into a bottom bore of a second sleeve and press fitting a fourth ball bearing into a top bore of the second sleeve to make a subassembly, stacking on the shaft subassembly the first sleeve subassembly, a spacer, and second sleeve subassembly and applying an axial load to the first sleeve subassembly, a spacer, and second sleeve subassembly to press fit the first sleeve subassembly, a spacer, and second sleeve subassembly to the shaft assembly to form a complete dual actuator pivot assembly.
Another aspect of the present invention is that the method further includes vibrating the complete dual actuator pivot assembly at a low amplitude simultaneously while applying the axial load.
Another aspect of the present invention is that the method further including measuring the frequency spectrum for the vibrating complete dual actuator pivot assembly to obtain a resonance frequency for the first sleeve subassembly and for the second sleeve subassembly.
Another aspect of the present invention is that the method further includes adjusting the axial load while measuring the frequency spectrum for the vibrating complete dual actuator pivot assembly to select a desired resonance frequency for the first sleeve subassembly and for the second sleeve subassembly.
Another aspect of the present invention is that the method further includes chilling the shaft assembly before stacking on the shaft subassembly the first sleeve subassembly, a spacer, and second sleeve subassembly.
Another aspect of the present invention is that the method further includes heating the first sleeve subassembly, a spacer, and second sleeve subassembly before stacking on the shaft subassembly.
Another aspect of the present invention is that the method further includes initially forming steps on the shaft, wherein the steps are formed to have diameters matching bearing bore diameters graded from large to small going from a first end of the shaft to a second end of the shaft.
Another aspect of the present invention is that the steps match bearing bore diameters graded from large to small going from the bottom to the top of the shaft so that the bearings at the bottom of the shaft do not produce high frictional forces against the full length of the shaft during assembly.
Another aspect of the present invention is that the method further includes initially forming a flangeless shaft comprising large diameter areas formed at a first and second end of the shaft and a reduced diameter area between the large diameter areas.
Another aspect of the present invention is that the large diameter areas provide a interference press fit with the fourth ball bearing press fitted into the top bore of the second sleeve and with the first ball bearing press fitted at the shaft base and provide a snug slip fit at the reduced diameter area for the third ball bearing press fitted into the bottom bore of the second sleeve and the second ball bearing press fitted into a top bore of the first sleeve.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.